Again, the sure fire way to detect spam mail is the indicia (upper right, where the stamp would be). If it says "First Class", open it up. If it says "Standard", it's junk. The old Bulk Rate Mail mail was renamed to "Standard" some years ago at the urging of bulk mailers to improve open rates. No important mail will is ever sent Standard due to the 6% non-deliverability. Take it from me, an old-timer bulk mailer.